As shown in FIGS. 1-3, a kitchen smoke exhausting device of the prior art comprises mainly a housing 10, a bellows 11, a motor 12, an impeller 13, a motor housing 14, a grease collecting tray 15, a liner 16, a bottom plate 17, a grease collecting cup 18, and a smoke discharging pipe 19. It is readily apparent that such a prior art kitchen smoke exhauster as described above comprises many component parts and is rather complicated in construction. In other words, the prior art kitchen smoke exhauster described above is not cost-effective.